The present invention concerns a rammer for an artillery piece with a barrel that can be elevated. The rammer has a cradle upstream of the barrel. The cradle has an accommodation for the shell aligned with the powder chamber, travels subject to a guide along a track that parallels the axis of the barrel, is coupled to a piston-and-cylinder mechanism that accelerates it toward the barrel, and is provided with a brake that brakes it at a prescribed distance upstream of the end of the barrel. The shell accommodation has a structure at the upstream end that engages the shell. The piston-and-cylinder mechanism is controlled by pneumatic controls that accommodate a rapid-opening valve. The valve diverts air back and forth between a source of compressed air and a vent.
A shell rammer of this type is described in EP 0 352 584 B1. Known rammers of this type are operated at a constant ramming pressure of 25 bars for example over the total range of elevation (xe2x88x922.5 to +65). At lower elevations this leads to unnecessarily high stress on both the rammer and the shell.
Furthermore, the shell-ramming forces are highly dependent on elevation, and increase considerably as elevation decreases. This situation can cause damage and can be a detriment to the precision of the ramming process.
The object of the present invention is an improved version of the aforesaid generic shell rammer wherein the ramming forces will not increase as rapidly when the elevation decreases and that will accordingly lack the aforesaid drawbacks.
This object is attained in accordance with the present invention by a pressure-reduction component with an electrically controlled proportional pressure-regulation valve between the source of compressed air and the rapid opening valve. Signals from a fire-direction system or position generator are forwarded to the electric controls. The pressure-regulation valve is then activated, reducing the ramming pressure in accordance with a prescribed formula as elevation decreases.
Advantageous advanced embodiments of the present invention will be specified hereinafter.
The theory behind the present invention is to reduce the ramming pressure acting on the piston-and-cylinder mechanism as elevation decreases and accordingly ensure that the ramming speeds remain within a prescribed range at different elevations.
It has been demonstrated that specific prescribed formulas representing the relationship between elevation and ramming pressure or ramming speed can be exploited to attain ramming forces as identical as possible over the total range of elevation. An attempt is made to ensure that the ramming speed determined at the maximal elevation and at the maximal ramming pressure established for that elevation will be maintained for the ramming process throughout the range of elevation.
Kinematics demonstrates that the formula for reducing ramming pressure or ramming speed as elevation decreases can be closely approximated by the equation
Vram=A+Bxc2x7Exe2x88x92Cxc2x7E2xe2x88x92Dxc2x7E3
wherein
Vram is the ramming speed in m/sec, E the angle of elevation in degrees, and
A=5.3-5.8
B=0.0516
C=0.000019
D=0.0000035,
are mathematically and empirically determined constants.
Calculations and testing have revealed that the most effective value for the dependence of ramming pressure on elevation is represented by the equation
Pram=12.6+0.3Exe2x88x920.000193xc2x7E2xe2x88x920.000012xc2x7E2
One embodiment of a shell rammer in accordance with the present invention will now be specified with reference to the accompanying drawing, wherein